jaxmat.state module

class AbstractState

Bases: Module

Abstract base class representing mechanical states.

add(**changes)

Utility method to add values such as new_state = state.add(stress=dsig).

update(**changes)

Utility method to update values such as new_state = state.update(stress=sig).

class SmallStrainState

Bases: AbstractState

State representation for small-strain behaviors.

This class stores the current strain \(\beps\) and stress \(\bsig\) tensors under the assumption of infinitesimal (small) deformations. It also supports internal state variables such as plastic strain, damage, or other material history quantities through the internal attribute.

internal

Nested state object representing internal variables (e.g., plastic strain, hardening variables, etc.). Defaults to None.

Type:

AbstractState, optional

strain

Symmetric second-order strain tensor \(\beps\) (small-strain assumption).

Type:

SymmetricTensor2

stress

Symmetric second-order Cauchy stress tensor \(\bsig\).

Type:

SymmetricTensor2

Notes

epsSymmetricTensor2

Alias for strain, allows accessing via state.eps.

sigSymmetricTensor2

Alias for stress, allows accessing via state.sig.

internal: AbstractState = None

strain: SymmetricTensor2 = SymmetricTensor2(dim=3, rank=2, _tensor=f64[3,3])

stress: SymmetricTensor2 = SymmetricTensor2(dim=3, rank=2, _tensor=f64[3,3])

property eps

Alias for strain.

property sig

Alias for stress.

PK1_to_PK2(F, PK1)

Convert the first Piola-Kirchhoff stress tensor (PK1) to the second Piola-Kirchhoff stress tensor (PK2). Enforce symmetry explicitly.

PK1_to_Cauchy(F, PK1)

Convert the first Piola-Kirchhoff stress tensor (PK1) to the Cauchy stress tensor. Enforce symmetry explicitly.

class FiniteStrainState

Bases: AbstractState

State representation for finite-strain continuum mechanics.

This class encapsulates the deformation gradient \(\bF\) (F) and first Piola-Kirchhoff stress \(\bP\) (PK1), along with optional internal variables. It provides convenience properties for converting between common stress measures: second Piola-Kirchhoff \(\bS\) (PK2) and Cauchy \(\bsig\) (sig) stresses.

internal

Nested internal state representing material history or additional constitutive information. Defaults to None.

Type:

AbstractState, optional

strain

Deformation gradient \(\bF\). Initialized as the identity tensor.

Type:

Tensor2

stress

First Piola-Kirchhoff stress tensor \(\bP\).

Type:

Tensor2

Notes

FTensor2

Alias for deformation gradient.

PK1Tensor2

Alias for first Piola-Kirchhoff stress tensor.

PK2SymmetricTensor2

Second Piola-Kirchhoff stress tensor \(\bS\), computed via PK1_to_PK2().

sigSymmetricTensor2

Cauchy stress tensor \(\bsig\), computed via PK1_to_Cauchy().

CauchySymmetricTensor2

Alias for sig.

internal: AbstractState = None

strain: Tensor2 = Tensor2(dim=3, rank=2, _tensor=f64[3,3])

stress: Tensor2 = Tensor2(dim=3, rank=2, _tensor=f64[3,3])

property F

property PK1

property PK2

property sig

property Cauchy

make_batched(module, Nbatch)

Broadcasts all leaf arrays of a single unbatched module into a batched version.

Parameters:

• module (Module) – An instance of an equinox Module (e.g., State) with array leaves.

• Nbatch (int) – The number of batch items to broadcast.

Return type:

Module

Returns:

A new instance of the same class, with each array field having shape (Nbatch, …).